At present there are commercially available hair curlers that are heated by slipping them onto special appendixes of apparatuses fitted with electric resistors. In some other cases, such apparatuses contain a liquid that is heated up when the hair curler is introduced in a heat source.
Commercially available hair curlers of the aforesaid and still other kinds have the task of releasing heat slowly to the hair that is wound thereupon in such manner as to give a hair-set without having to use an electric hair dryer.
Italian Utility Model No. 0 197 245 discloses a type of the above discussed hair curlers, consisting of a full body of cylindrical shape on which a net is applied after winding it on a lock of hair so as to hold it firmly. According to this disclosure, the cylindrical body of the hair curlers made of a material such that the hair curler can simply be immersed in hot water to gain heat quickly and then release it later in a sufficiently elongated period of time once it is positioned on the lock of hair, thereby attaining the desired hair-set. The main advantages of such a hair curler are its simple construction and extremely easy use, as it does not require the utilisation of electric appliances to be heated up, nor does it need to be filled with heating liquids or other materials. However, this prior art hair curler has turned out to be scarcely efficient in creating curls of hair, as the hair comes out simply undulated, without long-lasting curls. To attain curls, it is necessary to wind the locks of hair in helical manner on the hair curler and not simply in circles as disclosed in Italian Utility Model No. 0 197 245.